This invention relates generally to the field of solar cells, and more particularly to improvements in vertical junction solar cells.
The basic structure and operation of solar cells is well known, and the utilization of silicon solar cells for the generation of electricity for remote marine, terrestrial, and satellite applications is well documented. The development of the vertical junction solar cell answered the need for a radiation resistant cell having improved electrical conversion efficiency for operation in an ionizing radiation environment to which the cell may be subjected in extra-terrestrial applications. The state of the art relating to vertical junction solar cells may be exemplified by solar cell configurations disclosed by or referenced in U.S. Pat. No. 3,690,953 to Wise, entitled "Vertical Junction Hardened Solar Cell", and U.S. Pat. No. 3,985,579 to Rahilly, entitled "Rib and Channel Vertical Multijunction Solar Cell".
Vertical junction solar cells finding substantial prior use have structural fragility which has made them susceptible to failure when subjected to thermal cycling or to mechanical stresses within a power system. Existing vertical junction cell structure configurations comprise a plurality of narrow grooves or channels etched in the surface of a semiconductor substrate, the channels providing the areas upon which the photovoltaic junction of the cell is diffused. The narrow ribs of the existing cells are susceptible to fracture, severely limiting the reliability of the cells.
The present invention provides a novel vertical junction solar cell structure comprising a silicon chip having in one surface a plurality of holes closely spaced in an array to provide the vertical junction areas on the walls of the holes. This configuration substantially eliminates any rib fracture problem characteristic of grooved cells.
It is therefore an object of this invention to provide a more reliable radiation resistant silicon solar cell of improved efficiency.
It is a further object of this invention to provide a vertical junction solar cell having improved mechanical strength and light-absorbing characteristics.
These and other objects of the present invention will become apparent as the detailed description of representative embodiments thereof proceeds.